**Sergey Grigoriev 1, Alexey Vereschaka 2,\*, Filipp Milovich 3, Nikolay Sitnikov 4, Nikolay Andreev 3, Jury Bublikov 2, Catherine Sotova <sup>1</sup> and Ilya Sadov <sup>1</sup>**


Received: 3 November 2020; Accepted: 8 December 2020; Published: 10 December 2020

**Abstract:** The paper presents the results of studies focused on the specific features typical for the formation of the shape and structure of microdroplets embedded into the structure of the Ti–TiN–(Ti,Cr,Mo,Al)N and Ti–TiN–(Ti,Al,Nb,Zr)N coatings during their deposition. Three main microdroplet shapes—a sphere, a tear, and a lens—have been considered. The specific features typical for the formation of secondary layered structures on the surface of some microdroplets have also been examined. As a result of the conducted investigations, with the use of scanning and transmission electron microscopy, the influence of microdroplets on the distortion of the nanolayer structure of the coatings was studied. A hypothesis has been proposed concerning a relationship between the microdroplet shape and the presence or absence of secondary structures and the microdroplet sizes and weight, as well as the conditions in the unit chamber during the movement of a microdroplet from a cathode to the deposition surface. Based on the study focused on the shape of the microdroplet core and the specific features typical for the formation of the secondary structure around it, a hypothesis has been proposed, according to which, for some microdroplets, it takes much more time than previously assumed for the movement from a cathode to the deposition surface.

**Keywords:** nanolayered PVD coating; microdroplets; crack formation; tool wear
